1. Field of the Invention
This invention relates to a pipet cleaning apparatus for use in various experiments such as biological testing, chemical testing and in laboratories.
2. Description of the Prior Art
Generally, the pipet cleaning is carried out after the chemical pretreatment in a cleaning tank, and it is conventional to use a cleaning apparatus constructed as shown in FIG. 12. This known cleaning apparatus has a structure in which a pipe line B for feeding cleaning liquid and another pipe line C for discharging the used cleaning liquid (hereinafter called "waste liquid") out of a cleaning tank A are respectively connected with the cleaning tank A, and an overflow portion D of the same level as the full liquid level L.sub.1 established in the cleaning tank A is formed in the discharging pipe line C.
With respect to the cleaning operation, a liquid feeding cock E is opened for feeding the cleaning liquid (water) from the pipe line B to the cleaning tank A to fill it. At the same time, the liquid level in the discharging pipe line C is raised, and as the cleaning liquid overflows through the overflow portion D when the liquid level in the tank reaches the established full liquid level L.sub.1, the waste liquid flows down through the discharging pipe line C. Thus, by repeating the operation, the required number of immersion cleaning times (several or over ten times) is applied to the pipet.
In this connection, when the number of pipet cleaning times is set at ten, for example, it is necessary to stop the feed of cleaning liquid after completing the established ten times of cleaning in order to save the cleaning liquid or solvent. For that purpose, as a control system of the number of cleaning times, two kinds of systems have been proposed up to the present, i.e., a timer count type based on cleaning time corresponding to the number of cleaning times and a flow quantity count type on the basis of the used quantity of liquid corresponding to the number of cleaning times. In either of these two systems, however, the liquid level in the tank at the time of stopping the count (or the moment of completing the final cleaning) is not taken into consideration, and accordingly, there exist disvantages described hereinafter.
In case that the number of cleaning times is set at 10, for example, it is desired that at the time of completing the 10th (final) cleaning, the used cleaning liquid in the tank is still kept at the full liquid level without being discharged through the discharging pipe line C so that the pipet may still be kept immersed in the cleaning liquid. This is because it is necessary to prevent the cleaned pipet from being stuck by water spoor, dust or various germs in the air.
This requirement is not satisfied by either of the aforementioned two known control systems, because according to these systems, at the time of completing final cleaning, the liquid in the tank is drawn into the discharging pipe line C, once the liquid level in the tank reaches the full liquid level L.sub.1 and the completion of cleaning comes when the tank becomes empty.
Furthermore, during repeated cleaning, even when the waste liquid is drawn into the discharging pipe line C, the new cleaning liquid is fed from the feeding pipe line B to the cleaning tank A. Accordingly, the new cleaning liquid flows into the tank while discharging with the waste liquid drawn into the discharging pipe without being used for the pipet cleaning, this results in the cleaning liquid or solvent wastage and an increase of discharging time, bringing about a cost increase in cleaning and redundancy of cycle time from cleaning to discharge.